Mention 'sync_keywords_labels' in docs

Author: leplatrem

docs/actions.md

@@ -152,6 +152,7 @@ linked Jira issue status to "Closed". If the bug changes to a status not listed
 - `maybe_update_issue_resolution`
 - `maybe_update_issue_status`
 - `create_comment`
+- `sync_keywords_labels`
 - `sync_whiteboard_labels`
 - `maybe_update_components`: looks at the component that's set on the bug (if any) and any components added to the project configuration with the `jira_components` parameter (see above). If those components are available on the Jira side as well, they're added to the Jira issue